1. Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method and device for signal transmission in a wireless communication system.
2. Related Art
In next generation multimedia mobile communication systems, there is a demand for a system capable of processing and transmitting a variety of information (e.g., video and radio data) in addition to the early-stage voice service. The wireless communication system is designed for the purpose of providing reliable communication to a plurality of users irrespective of their locations and mobility. However, a wireless channel has an abnormal characteristic such as a fading phenomenon caused by a path loss, noise, and multipath, an inter-symbol interference (ISI), a Doppler effect caused by mobility of a mobile station (MS), etc. Various techniques have been developed to overcome the abnormal characteristic of the wireless channel and to increase reliability of wireless communication.
In general, a sequence is used for various channels and signals such as a synchronization signal, a scrambling code, etc. The sequence used in the wireless communication system must satisfy the following properties.
(1) Good correlation property for providing high detection capability
(2) Low peak-to-average power ratio (PAPR)/cubic metric (CM) for increasing efficiency of a power amplifier
(3) High capacity of a sequence for facilitating various information transmission or cell planning.
A reference signal (RS) is used in channel estimation. The channel estimation is required for user scheduling and/or data demodulation. The RS is a signal which is known to both a transmitter and a receiver, and is also referred to as a pilot.
In order to obtain a gain in channel estimation capability, a signal consisting of only RSs such as a preamble can be used. Since density of the RSs is high, the channel estimation capability can be improved. In general, the RSs are transmitted together with data subcarriers to increase a data transfer amount. However, this method may result in deterioration of the channel estimation performance in comparison with the former method since density of the RSs is decreased.
PAPR/CM characteristics are one of important factors in the signal design in association with battery consumption. A method and device for signal transmission having a low PAPR/CM characteristic are required.